Nipple Waterer

Only about half of our 6 chicks use the nipple waterer after we put it in this weekend. They had a standard chick waterer with the upside down bottle and the trough thing from 3 days old until yesterday when they turned about 4 weeks old. I have tried tapping the nipples and letting them get the water off my finger and watching it drop to the ground but several of them just don't get it. I remove the old water for and hour or so and then worry that they need water so I put it back in there, any advice would be great..

the one thing my grandfather told me is that baby animals are smarter than any baby human. if you remover the waterer and leave the nipple waterer the chicks will figure it out eventualy they are pretty smart. just keep and eye on them and make sure they dont start getting too week